Individualssuccessful at weight loss maintenance WTLM utilize similar behaviors but invarying amounts and combinations. Research identifying characteristics whichpredict WTLM success could be used to develop effective WTLM treatmentprograms. The purpose of this retrospective analysis was to determinebehavioral e.g., self monitoring of dietary intake and biological factorse.g., sex which may influence WTLM success. Methods: In a previouslyconducted 12-month WTLM study, weight-reduced middle-aged and older men andwomen n = 39 were assigned behavioral goals and asked to daily self-monitorbody weight, fruit and vegetable intake, water consumption, and physicalactivity. This investigation utilized a crisp set qualitative comparativeanalysis QCA to characterize individuals’ weight changes and behaviors. Sexdifference in clinically significant weight loss WL ≥5% WL at 12 monthswas investigated, and growth curve models estimated interaction effects betweensex and WTLM predictors. Results: QCA findings suggest patterns of weightchange during the initial three months of WTLM treatment may dictate 12-monthweight outcomes. No sex difference was found in clinically significant WL or inthe interaction of sex and behaviors on weight change. Conclusions: WTLMtreatments should provide more intensive support during transition from WL toWTLM, particularly during the first three months.